1. Field of the Invention
The present invention relates to a piezoelectric oscillator used for generating a clock signal in telecommunication equipment, electronic equipment, or the like.
2. Description of the Related Art
Clock signal generators (timing devices) for portable communication units and the like have conventionally employed piezoelectric oscillators such as a temperature-compensated quartz-crystal oscillator.
As shown in FIG. 15, for example, in the conventional temperature-compensated quartz-crystal oscillator, a package 23 accommodating a quartz-crystal oscillation device therein is attached on a supporting substrate 21 having a recess 25 in a central region on a top face thereof and a plurality of external terminals on a bottom face thereof. The known oscillator is configured so that an IC device 26 for outputting an oscillation signal on the basis of oscillation of the quartz-crystal oscillation device is accommodated in a region surrounded by a bottom face of the package 23 and inner side faces of the recess 25 (refer to Japanese Unexamined Patent Publication No. 10(1998)-98151).
The package 23 and the supporting substrate 21 are normally formed from a ceramic material such as alumina ceramics and manufactured by using a conventionally known green sheet lamination method. On the bottom face of the package 23 and a top face of the supporting substrate 21, respectively, there are provided a plurality of connection electrodes 24 at their corresponding locations and the package 23 is fixed to the top face of the supporting substrate 21 by bonding these connection electrodes 24 to each other by way of a conductive bonding material.
However, in the above-mentioned conventional piezoelectric oscillator, oxidization corrosion of metal bodies forming connection electrodes 24 cannot prevent and reliability of the piezoelectric oscillator cannot be fully maintained.
Moreover, since the recess 25 having a dimension large enough to accommodate the IC device 26 needs to be formed in the supporting substrate 21, the area of the supporting substrate 21 becomes larger than IC device 26 in both of the lengthwise and breadthwise directions, thereby making miniaturization of the piezoelectric oscillator difficult.
Further, due to the recess 25, it is impossible to make the most of the region on the surface of the supporting substrate 21 in which the connection electrodes 24 do not exist. That is, the level difference of the recess 25 leads to an disadvantage that the IC device and other electronic parts cannot be mounted.
An object of the present invention is to provide a piezoelectric oscillator in which oxidative corrosion of metal bodies can be prevented.
Another object of the present invention is to provide a piezoelectric oscillator capable of reducing its whole configuration in size and making the most of the surface of the supporting substrate.